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  <div class="section" id="controllers">
<h1><a class="toc-backref" href="#id1">Controllers</a><a class="headerlink" href="#controllers" title="Permalink to this headline">¶</a></h1>
<p>Controllers are the heart of your application, as they determine how
HTTP requests should be handled.</p>
<div class="contents topic" id="page-contents">
<p class="topic-title first">Page Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#controllers" id="id1">Controllers</a><ul>
<li><a class="reference internal" href="#what-is-a-controller" id="id2">What is a Controller?</a></li>
<li><a class="reference internal" href="#let-s-try-it-hello-world" id="id3">Let&#8217;s try it: Hello World!</a></li>
<li><a class="reference internal" href="#methods" id="id4">Methods</a></li>
<li><a class="reference internal" href="#passing-uri-segments-to-your-methods" id="id5">Passing URI Segments to your methods</a></li>
<li><a class="reference internal" href="#defining-a-default-controller" id="id6">Defining a Default Controller</a></li>
<li><a class="reference internal" href="#remapping-method-calls" id="id7">Remapping Method Calls</a></li>
<li><a class="reference internal" href="#processing-output" id="id8">Processing Output</a></li>
<li><a class="reference internal" href="#private-methods" id="id9">Private methods</a></li>
<li><a class="reference internal" href="#organizing-your-controllers-into-sub-directories" id="id10">Organizing Your Controllers into Sub-directories</a></li>
<li><a class="reference internal" href="#class-constructors" id="id11">Class Constructors</a></li>
<li><a class="reference internal" href="#reserved-method-names" id="id12">Reserved method names</a></li>
<li><a class="reference internal" href="#that-s-it" id="id13">That&#8217;s it!</a></li>
</ul>
</li>
</ul>
</div>
<div class="section" id="what-is-a-controller">
<h2><a class="toc-backref" href="#id2">What is a Controller?</a><a class="headerlink" href="#what-is-a-controller" title="Permalink to this headline">¶</a></h2>
<p><strong>A Controller is simply a class file that is named in a way that can be
associated with a URI.</strong></p>
<p>Consider this URI:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">blog</span><span class="o">/</span>
</pre></div>
</div>
<p>In the above example, CodeIgniter would attempt to find a controller
named Blog.php and load it.</p>
<p><strong>When a controller&#8217;s name matches the first segment of a URI, it will
be loaded.</strong></p>
</div>
<div class="section" id="let-s-try-it-hello-world">
<h2><a class="toc-backref" href="#id3">Let&#8217;s try it: Hello World!</a><a class="headerlink" href="#let-s-try-it-hello-world" title="Permalink to this headline">¶</a></h2>
<p>Let&#8217;s create a simple controller so you can see it in action. Using your
text editor, create a file called Blog.php, and put the following code
in it:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="o">&lt;?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">Blog</span> <span class="k">extends</span> <span class="nx">CI_Controller</span> <span class="p">{</span>

        <span class="k">public</span> <span class="k">function</span> <span class="nf">index</span><span class="p">()</span>
        <span class="p">{</span>
                <span class="k">echo</span> <span class="s1">&#39;Hello World!&#39;</span><span class="p">;</span>
        <span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Then save the file to your <em>application/controllers/</em> directory.</p>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">The file must be called &#8216;Blog.php&#8217;, with a capital &#8216;B&#8217;.</p>
</div>
<p>Now visit the your site using a URL similar to this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">blog</span><span class="o">/</span>
</pre></div>
</div>
<p>If you did it right, you should see:</p>
<blockquote>
<div>Hello World!</div></blockquote>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">Class names must start with an uppercase letter.</p>
</div>
<p>This is valid:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="o">&lt;?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">Blog</span> <span class="k">extends</span> <span class="nx">CI_Controller</span> <span class="p">{</span>

<span class="p">}</span>
</pre></div>
</div>
<p>This is <strong>not</strong> valid:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="o">&lt;?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">blog</span> <span class="k">extends</span> <span class="nx">CI_Controller</span> <span class="p">{</span>

<span class="p">}</span>
</pre></div>
</div>
<p>Also, always make sure your controller extends the parent controller
class so that it can inherit all its methods.</p>
</div>
<div class="section" id="methods">
<h2><a class="toc-backref" href="#id4">Methods</a><a class="headerlink" href="#methods" title="Permalink to this headline">¶</a></h2>
<p>In the above example the method name is <tt class="docutils literal"><span class="pre">index()</span></tt>. The &#8220;index&#8221; method
is always loaded by default if the <strong>second segment</strong> of the URI is
empty. Another way to show your &#8220;Hello World&#8221; message would be this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">blog</span><span class="o">/</span><span class="nx">index</span><span class="o">/</span>
</pre></div>
</div>
<p><strong>The second segment of the URI determines which method in the
controller gets called.</strong></p>
<p>Let&#8217;s try it. Add a new method to your controller:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="o">&lt;?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">Blog</span> <span class="k">extends</span> <span class="nx">CI_Controller</span> <span class="p">{</span>

        <span class="k">public</span> <span class="k">function</span> <span class="nf">index</span><span class="p">()</span>
        <span class="p">{</span>
                <span class="k">echo</span> <span class="s1">&#39;Hello World!&#39;</span><span class="p">;</span>
        <span class="p">}</span>

        <span class="k">public</span> <span class="k">function</span> <span class="nf">comments</span><span class="p">()</span>
        <span class="p">{</span>
                <span class="k">echo</span> <span class="s1">&#39;Look at this!&#39;</span><span class="p">;</span>
        <span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Now load the following URL to see the comment method:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">blog</span><span class="o">/</span><span class="nx">comments</span><span class="o">/</span>
</pre></div>
</div>
<p>You should see your new message.</p>
</div>
<div class="section" id="passing-uri-segments-to-your-methods">
<h2><a class="toc-backref" href="#id5">Passing URI Segments to your methods</a><a class="headerlink" href="#passing-uri-segments-to-your-methods" title="Permalink to this headline">¶</a></h2>
<p>If your URI contains more than two segments they will be passed to your
method as parameters.</p>
<p>For example, let&#8217;s say you have a URI like this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">products</span><span class="o">/</span><span class="nx">shoes</span><span class="o">/</span><span class="nx">sandals</span><span class="o">/</span><span class="mi">123</span>
</pre></div>
</div>
<p>Your method will be passed URI segments 3 and 4 (&#8220;sandals&#8221; and &#8220;123&#8221;):</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="o">&lt;?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">Products</span> <span class="k">extends</span> <span class="nx">CI_Controller</span> <span class="p">{</span>

        <span class="k">public</span> <span class="k">function</span> <span class="nf">shoes</span><span class="p">(</span><span class="nv">$sandals</span><span class="p">,</span> <span class="nv">$id</span><span class="p">)</span>
        <span class="p">{</span>
                <span class="k">echo</span> <span class="nv">$sandals</span><span class="p">;</span>
                <span class="k">echo</span> <span class="nv">$id</span><span class="p">;</span>
        <span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">If you are using the <a class="reference internal" href="routing.html"><em>URI Routing</em></a>
feature, the segments passed to your method will be the re-routed
ones.</p>
</div>
</div>
<div class="section" id="defining-a-default-controller">
<h2><a class="toc-backref" href="#id6">Defining a Default Controller</a><a class="headerlink" href="#defining-a-default-controller" title="Permalink to this headline">¶</a></h2>
<p>CodeIgniter can be told to load a default controller when a URI is not
present, as will be the case when only your site root URL is requested.
To specify a default controller, open your <strong>application/config/routes.php</strong>
file and set this variable:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nv">$route</span><span class="p">[</span><span class="s1">&#39;default_controller&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s1">&#39;blog&#39;</span><span class="p">;</span>
</pre></div>
</div>
<p>Where &#8216;blog&#8217; is the name of the controller class you want used. If you now
load your main index.php file without specifying any URI segments you&#8217;ll
see your &#8220;Hello World&#8221; message by default.</p>
<p>For more information, please refer to the &#8220;Reserved Routes&#8221; section of the
<a class="reference internal" href="routing.html"><em>URI Routing</em></a> documentation.</p>
</div>
<div class="section" id="remapping-method-calls">
<h2><a class="toc-backref" href="#id7">Remapping Method Calls</a><a class="headerlink" href="#remapping-method-calls" title="Permalink to this headline">¶</a></h2>
<p>As noted above, the second segment of the URI typically determines which
method in the controller gets called. CodeIgniter permits you to override
this behavior through the use of the <tt class="docutils literal"><span class="pre">_remap()</span></tt> method:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">public</span> <span class="k">function</span> <span class="nf">_remap</span><span class="p">()</span>
<span class="p">{</span>
        <span class="c1">// Some code here...</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">If your controller contains a method named _remap(),
it will <strong>always</strong> get called regardless of what your URI contains. It
overrides the normal behavior in which the URI determines which method
is called, allowing you to define your own method routing rules.</p>
</div>
<p>The overridden method call (typically the second segment of the URI) will
be passed as a parameter to the <tt class="docutils literal"><span class="pre">_remap()</span></tt> method:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">public</span> <span class="k">function</span> <span class="nf">_remap</span><span class="p">(</span><span class="nv">$method</span><span class="p">)</span>
<span class="p">{</span>
        <span class="k">if</span> <span class="p">(</span><span class="nv">$method</span> <span class="o">===</span> <span class="s1">&#39;some_method&#39;</span><span class="p">)</span>
        <span class="p">{</span>
                <span class="nv">$this</span><span class="o">-&gt;</span><span class="nv">$method</span><span class="p">();</span>
        <span class="p">}</span>
        <span class="k">else</span>
        <span class="p">{</span>
                <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">default_method</span><span class="p">();</span>
        <span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Any extra segments after the method name are passed into <tt class="docutils literal"><span class="pre">_remap()</span></tt> as an
optional second parameter. This array can be used in combination with
PHP&#8217;s <a class="reference external" href="http://php.net/call_user_func_array">call_user_func_array()</a>
to emulate CodeIgniter&#8217;s default behavior.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">public</span> <span class="k">function</span> <span class="nf">_remap</span><span class="p">(</span><span class="nv">$method</span><span class="p">,</span> <span class="nv">$params</span> <span class="o">=</span> <span class="k">array</span><span class="p">())</span>
<span class="p">{</span>
        <span class="nv">$method</span> <span class="o">=</span> <span class="s1">&#39;process_&#39;</span><span class="o">.</span><span class="nv">$method</span><span class="p">;</span>
        <span class="k">if</span> <span class="p">(</span><span class="nb">method_exists</span><span class="p">(</span><span class="nv">$this</span><span class="p">,</span> <span class="nv">$method</span><span class="p">))</span>
        <span class="p">{</span>
                <span class="k">return</span> <span class="nb">call_user_func_array</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="nv">$this</span><span class="p">,</span> <span class="nv">$method</span><span class="p">),</span> <span class="nv">$params</span><span class="p">);</span>
        <span class="p">}</span>
        <span class="nx">show_404</span><span class="p">();</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="processing-output">
<h2><a class="toc-backref" href="#id8">Processing Output</a><a class="headerlink" href="#processing-output" title="Permalink to this headline">¶</a></h2>
<p>CodeIgniter has an output class that takes care of sending your final
rendered data to the web browser automatically. More information on this
can be found in the <a class="reference internal" href="views.html"><em>Views</em></a> and <a class="reference internal" href="../libraries/output.html"><em>Output Class</em></a> pages. In some cases, however, you might want to
post-process the finalized data in some way and send it to the browser
yourself. CodeIgniter permits you to add a method named <tt class="docutils literal"><span class="pre">_output()</span></tt>
to your controller that will receive the finalized output data.</p>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">If your controller contains a method named <tt class="docutils literal"><span class="pre">_output()</span></tt>,
it will <strong>always</strong> be called by the output class instead of
echoing the finalized data directly. The first parameter of the
method will contain the finalized output.</p>
</div>
<p>Here is an example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">public</span> <span class="k">function</span> <span class="nf">_output</span><span class="p">(</span><span class="nv">$output</span><span class="p">)</span>
<span class="p">{</span>
        <span class="k">echo</span> <span class="nv">$output</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>Please note that your <tt class="docutils literal"><span class="pre">_output()</span></tt> method will receive the
data in its finalized state. Benchmark and memory usage data
will be rendered, cache files written (if you have caching
enabled), and headers will be sent (if you use that
<a class="reference internal" href="../libraries/output.html"><em>feature</em></a>) before it is handed off
to the <tt class="docutils literal"><span class="pre">_output()</span></tt> method.
To have your controller&#8217;s output cached properly, its
<tt class="docutils literal"><span class="pre">_output()</span></tt> method can use:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">if</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-&gt;</span><span class="na">output</span><span class="o">-&gt;</span><span class="na">cache_expiration</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">)</span>
<span class="p">{</span>
        <span class="nv">$this</span><span class="o">-&gt;</span><span class="na">output</span><span class="o">-&gt;</span><span class="na">_write_cache</span><span class="p">(</span><span class="nv">$output</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<p class="last">If you are using this feature the page execution timer and
memory usage stats might not be perfectly accurate since they
will not take into account any further processing you do.
For an alternate way to control output <em>before</em> any of the
final processing is done, please see the available methods
in the <a class="reference internal" href="../libraries/output.html"><em>Output Library</em></a>.</p>
</div>
</div>
<div class="section" id="private-methods">
<h2><a class="toc-backref" href="#id9">Private methods</a><a class="headerlink" href="#private-methods" title="Permalink to this headline">¶</a></h2>
<p>In some cases you may want certain methods hidden from public access.
In order to achieve this, simply declare the method as being private
or protected and it will not be served via a URL request. For example,
if you were to have a method like this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">private</span> <span class="k">function</span> <span class="nf">_utility</span><span class="p">()</span>
<span class="p">{</span>
        <span class="c1">// some code</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Trying to access it via the URL, like this, will not work:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">blog</span><span class="o">/</span><span class="nx">_utility</span><span class="o">/</span>
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Prefixing method names with an underscore will also prevent
them from being called. This is a legacy feature that is left
for backwards-compatibility.</p>
</div>
</div>
<div class="section" id="organizing-your-controllers-into-sub-directories">
<h2><a class="toc-backref" href="#id10">Organizing Your Controllers into Sub-directories</a><a class="headerlink" href="#organizing-your-controllers-into-sub-directories" title="Permalink to this headline">¶</a></h2>
<p>If you are building a large application you might want to hierarchically
organize or structure your controllers into sub-directories. CodeIgniter
permits you to do this.</p>
<p>Simply create sub-directories under the main <em>application/controllers/</em>
one and place your controller classes within them.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>When using this feature the first segment of your URI must
specify the folder. For example, let&#8217;s say you have a controller located
here:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="nx">application</span><span class="o">/</span><span class="nx">controllers</span><span class="o">/</span><span class="nx">products</span><span class="o">/</span><span class="nx">Shoes</span><span class="o">.</span><span class="nx">php</span>
</pre></div>
</div>
<p>To call the above controller your URI will look something like this:</p>
<div class="last highlight-ci"><div class="highlight"><pre><span class="nx">example</span><span class="o">.</span><span class="nx">com</span><span class="o">/</span><span class="nx">index</span><span class="o">.</span><span class="nx">php</span><span class="o">/</span><span class="nx">products</span><span class="o">/</span><span class="nx">shoes</span><span class="o">/</span><span class="nx">show</span><span class="o">/</span><span class="mi">123</span>
</pre></div>
</div>
</div>
<p>Each of your sub-directories may contain a default controller which will be
called if the URL contains <em>only</em> the sub-directory. Simply put a controller
in there that matches the name of your &#8216;default_controller&#8217; as specified in
your <em>application/config/routes.php</em> file.</p>
<p>CodeIgniter also permits you to remap your URIs using its <a class="reference internal" href="routing.html"><em>URI
Routing</em></a> feature.</p>
</div>
<div class="section" id="class-constructors">
<h2><a class="toc-backref" href="#id11">Class Constructors</a><a class="headerlink" href="#class-constructors" title="Permalink to this headline">¶</a></h2>
<p>If you intend to use a constructor in any of your Controllers, you
<strong>MUST</strong> place the following line of code in it:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="k">parent</span><span class="o">::</span><span class="na">__construct</span><span class="p">();</span>
</pre></div>
</div>
<p>The reason this line is necessary is because your local constructor will
be overriding the one in the parent controller class so we need to
manually call it.</p>
<p>Example:</p>
<div class="highlight-ci"><div class="highlight"><pre><span class="o">&lt;?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">Blog</span> <span class="k">extends</span> <span class="nx">CI_Controller</span> <span class="p">{</span>

        <span class="k">public</span> <span class="k">function</span> <span class="nf">__construct</span><span class="p">()</span>
        <span class="p">{</span>
                <span class="k">parent</span><span class="o">::</span><span class="na">__construct</span><span class="p">();</span>
                <span class="c1">// Your own constructor code</span>
        <span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Constructors are useful if you need to set some default values, or run a
default process when your class is instantiated. Constructors can&#8217;t
return a value, but they can do some default work.</p>
</div>
<div class="section" id="reserved-method-names">
<h2><a class="toc-backref" href="#id12">Reserved method names</a><a class="headerlink" href="#reserved-method-names" title="Permalink to this headline">¶</a></h2>
<p>Since your controller classes will extend the main application
controller you must be careful not to name your methods identically to
the ones used by that class, otherwise your local functions will
override them. See <a class="reference internal" href="reserved_names.html"><em>Reserved Names</em></a> for a full
list.</p>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">You should also never have a method named identically
to its class name. If you do, and there is no <tt class="docutils literal"><span class="pre">__construct()</span></tt>
method in the same class, then your e.g. <tt class="docutils literal"><span class="pre">Index::index()</span></tt>
method will be executed as a class constructor! This is a PHP4
backwards-compatibility feature.</p>
</div>
</div>
<div class="section" id="that-s-it">
<h2><a class="toc-backref" href="#id13">That&#8217;s it!</a><a class="headerlink" href="#that-s-it" title="Permalink to this headline">¶</a></h2>
<p>That, in a nutshell, is all there is to know about controllers.</p>
</div>
</div>


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